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From: COLE@USC-ISIB.ARPA
Newsgroups: net.micro.pc
Subject: Re: XT Configuration Question
Message-ID: <1729@sri-arpa.UUCP>
Date: Sat, 7-Jul-84 14:24:37 EDT
Article-I.D.: sri-arpa.1729
Posted: Sat Jul  7 14:24:37 1984
Date-Received: Tue, 10-Jul-84 07:41:41 EDT
Lines: 20

From:  Randy Cole <COLE@USC-ISIB.ARPA>

I think you have been misled about the location of the boot ROM for hard
disk controllers.  I have a Kamerman Labs system, which uses a Data
Technology Corp. (DTC) controller.  The ROM is located on the controller
board.  I am sure the Western Digital controller also has the ROM on board.
What happens is that during the boot process, newer PCs (the so-called PC2s,
which use 64K RAMs on their motherboard) and XTs look for adapter cards with
program ROM, starting at C8000 hex and looking at 2K increments through
F4000 hex.  The code in the ROMs must start with a hex 55, then a hex AA, and
then obey a few other rules.  If the PC or XT finds such ROM code it will do
a jump far to byte 3 of the ROM, allowing the controller or whatever to hook
itself into the system.

The DTC controller is a DTC-5150 BX.  Western Digitals is a WD1002-WX2 (I
think).  They both cost $295 and the Western Digital can be bought from
Kierulff in the LA area.

Randy Cole
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